Apparatus and methods for managing hyper frame number (HFN) de-synchronization in radio link control (RLC) unacknowledged mode (UM)

ABSTRACT

Apparatus and methods of data communication between a transmitter and a receiver in a radio link control (RLC) unacknowledged mode (UM) include determining, by the transmitter, a hyper frame number (HFN) de-synchronization condition, wherein the HFN de-synchronization condition is FALSE when at least one protocol data unit (PDU) out of a plurality of successive PDUs is successfully transmitted by the transmitter to the receiver, and wherein the HFN de-synchronization condition is TRUE when all of the plurality of successive PDUs are lost, and adjusting, by the transmitter, a transmitter HFN of the transmitter when the HFN de-synchronization condition is TRUE, wherein the adjusted transmitter HFN is used for new PDUs to be transmitted.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application for patent claims priority to U.S. ProvisionalApplication No. 61/712,120 entitled “METHOD FOR DETECTING AND CORRECTINGHYPER FRAME NUMBER (HFN) DE-SYNCHRONIZATION IN RADIO LINK CONTROL (RLC)UNACKNOWLEDGED MODE (UM) ON HIGH SPEED PACKET ACCESS (HSPA) CHANNELS”filed Oct. 10, 2012, and assigned to the assignee hereof and herebyexpressly incorporated by reference herein.

BACKGROUND

1. Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to managing hyper framenumber (HFN) de-synchronization in radio link control (RLC)unacknowledged mode (UM).

2. Background

Wireless communication networks are widely deployed to provide variouscommunication services such as telephony, video, data, messaging,broadcasts, and so on. Such networks, which are usually multiple accessnetworks, support communications for multiple users by sharing theavailable network resources. One example of such a network is the UMTSTerrestrial Radio Access Network (UTRAN). The UTRAN is the radio accessnetwork (RAN) defined as a part of the Universal MobileTelecommunications System (UMTS), a third generation (3G) mobile phonetechnology supported by the 3rd Generation Partnership Project (3GPP).UMTS, which is the successor to Global System for Mobile Communications(GSM) technologies, currently supports various air interface standards,such as Wideband-Code Division Multiple Access (W-CDMA), TimeDivision-Code Division Multiple Access (TD-CDMA), and TimeDivision-Synchronous Code Division Multiple Access (TD-SCDMA). UMTS alsosupports enhanced 3G data communications protocols, such as High SpeedPacket Access (HSPA), which provides higher data transfer speeds andcapacity to associated UMTS networks.

In W-CDMA, RLC unacknowledged mode (UM) is a radio link protocol inwhich a success or failure of the received protocol data units (PDUs)are not acknowledged. RLC UM may be used for real-time or near-real-timeapplications as well as delay-sensitive applications. In RLC UM,ciphering and deciphering are performed on transmitted packets byutilizing a time-varying parameter value or count referred to asCOUNT-C, which is a combination of a short sequence number (SN) and along SN. The short SN is a 7-bit RLC SN that is part of the RLC UMprotocol data unit (PDU) header. The long SN is a 25-bit RLC UM HFN thatis incremented at each RLC SN cycle. Accordingly, upon transmittingevery 127 consecutive RLC UM PDUs, an RLC SN cycle at the transmittingRLC UM entity is completed, the RLC SN at the transmitting RLC UM entitywraps around, and the HFN at the transmitting RLC UM entity isincremented. Meanwhile, if the receiving RLC UM entity misses more than127 consecutive PDUs, because the receiving RLC UM entity is not awareof the missed PDUs, the HFN at the receiving RLC UM entity is notincremented, resulting in a de-synchronization between the HFNs at thetransmitting and receiving RLC UM entities. Thereafter, if further RLCUM PDUs are transmitted and received correctly, due to thede-synchronization between the HFNs at the transmitting and receivingRLC UM entities, the data in the received RLC UM PDUs will beerroneously deciphered at the receiving RLC UM entity, and since thetransmitting and receiving RLC UM entities will not be able to detectsuch error, the corrupted PDUs will just be forwarded to higher layers.Accordingly, in RLC UM, HFN de-synchronization can result in incorrectservice data unit (SDU) generation or garbled voice in, e.g., voice overHSPA applications.

As the demand for mobile broadband access continues to increase,research and development continue to advance the UMTS technologies notonly to meet the growing demand for mobile broadband access, but toadvance and enhance the user experience with mobile communications.Thus, in this case, improved apparatus and methods are desired formanaging HFN de-synchronization in RLC UM.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to apparatus and methodfor managing HFN de-synchronization in RLC UM.

In one aspect, a method of data communication between a transmitter anda receiver in an RLC UM is provided that includes determining, by thetransmitter, an HFN de-synchronization condition, wherein the HFNde-synchronization condition is FALSE when at least one PDU out of aplurality of successive PDUs is successfully transmitted by thetransmitter to the receiver, and wherein the HFN de-synchronizationcondition is TRUE when all of the plurality of successive PDUs are lost,and adjusting, by the transmitter, a transmitter HFN of the transmitterwhen the HFN de-synchronization condition is TRUE, wherein the adjustedtransmitter HFN is used for new PDUs to be transmitted.

In one aspect, a computer program product for data communication betweena transmitter and a receiver in an RLC UM is provided that includes acomputer-readable medium, including code for determining, by thetransmitter, an HFN de-synchronization condition, wherein the HENde-synchronization condition is FALSE when at least one PDU out of aplurality of successive PDUs is successfully transmitted by thetransmitter to the receiver, and wherein the HFN de-synchronizationcondition is TRUE when all of the plurality of successive PDUs are lost,and code for adjusting, by the transmitter, a transmitter HFN of thetransmitter when the HFN de-synchronization condition is TRUE, whereinthe adjusted transmitter HFN is used for new PDUs to be transmitted.

In one aspect, an apparatus for data communication between a transmitterand a receiver in an RLC UM is provided that includes means fordetermining, by the transmitter, an HFN de-synchronization condition,wherein the HFN de-synchronization condition is FALSE when at least onePDU out of a plurality of successive PDUs is successfully transmitted bythe transmitter to the receiver, and wherein the HFN de-synchronizationcondition is TRUE when all of the plurality of successive PDUs are lost,and means for adjusting, by the transmitter, a transmitter HFN of thetransmitter when the HFN de-synchronization condition is TRUE, whereinthe adjusted transmitter HFN is used for new PDUs to be transmitted.

In one aspect, an apparatus for data communication between a transmitterand a receiver in an RLC UM is provided that includes at least oneprocessor, and a memory coupled to the at least one processor, whereinthe at least one processor is configured to determine, by thetransmitter, an HFN de-synchronization condition, wherein the HFNde-synchronization condition is FALSE when at least one PDU out of aplurality of successive PDUs is successfully transmitted by thetransmitter to the receiver, and wherein the HFN de-synchronizationcondition is TRUE when all of the plurality of successive PDUs are lost,and adjust, by the transmitter, a transmitter HFN of the transmitterwhen the HFN de-synchronization condition is TRUE, wherein the adjustedtransmitter HFN is used for new PDUs to be transmitted.

These and other aspects of the disclosure will become more fullyunderstood upon a review of the detailed description, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects will hereinafter be described in conjunction withthe appended drawings, provided to illustrate and not to limit thedisclosed aspects, wherein like designations denote like elements, andin which:

FIG. 1 is a schematic block diagram of one aspect of a system formanaging HFN de-synchronization in RLC UM;

FIG. 2 is a flowchart of one aspect of a method of the system of FIG. 1;

FIG. 3 is a block diagram illustrating an example of a hardwareimplementation for an apparatus of FIG. 1 employing a processing system;

FIG. 4 is a block diagram conceptually illustrating an example of atelecommunications system including aspects of the system of FIG. 1;

FIG. 5 is a conceptual diagram illustrating an example of a radioprotocol architecture for the user and control planes in aspects of thesystem of FIG. 1;

FIG. 6 is a conceptual diagram illustrating an example of an accessnetwork including aspects of the system of FIG. 1; and

FIG. 7 is a block diagram conceptually illustrating an example of a NodeB in communication with a UE in a telecommunications system includingaspects of the system of FIG. 1.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

According to some aspects of the present disclosure, methods andapparatus are provided that detect and correct HFN de-synchronization inRLC UM. A transmitter that is communicating with a receiver in RLC UMmay determine a condition of HFN de-synchronization, and if HFNde-synchronization is present, the transmitter may update or adjust atransmitter HFN to ensure that ciphering parameters are synchronizedwith the receiver. Accordingly, with HFN de-synchronization detectionand enhanced HFN updating and synchronization in RLC UM, the transmittercan ensure that the transmitter HFN is the same as the receiver HFN sothat correct SDUs can be deciphered out of received RLC UM PDUs at thereceiver. In an aspect, this may result in a reduction of dropped callsdue to wrong SDUs (internet protocol (IP) frames) during packet calls,and may also result in avoiding garbled voice during circuit switched(CS) calls when RLC UM entity is used over HSPA channels or voice overIP (VoIP) is used over HSPA channels. While the present description ispresented primarily with reference to the HSPA radio technology, thedescription may also be applied to other radio technologies (e.g., longterm evolution (LTE)) when those other technologies are in RLC UM.

Referring to FIG. 1, in one aspect, system 1000 includes firstcommunications apparatus 1002 that is communicating with secondcommunications apparatus 1004. First communications apparatus 1002 andsecond communications apparatus 1004 are both operating in RLC UM, andrespectively include transmitting RLC UM entity 1006 and receiving RLCUM entity 1018. According to operation in RLC UM, transmitting RLC UMentity 1006 transmits packets to receiving RLC UM entity 1018 andperforms ciphering on the transmitted packets by utilizing transmitterRLC UM SN 1010 and transmitter HFN 1012. Correspondingly, according tooperation in RLC UM, receiving RLC UM entity 1018 deciphers the receivedpackets by utilizing receiver RLC UM SN 1024 and receiver HFN 1020.Accordingly, for successful deciphering of the received packets atreceiving RLC UM entity 1018, while receiver RLC UM SN 1024 isdetermined based on transmitter RLC UM SN 1010 that is part of the RLCUM PDU header in the received packets, receiver HFN 1020 has to besynchronized with transmitter HFN 1012 without explicit informationabout transmitter HFN 1012.

In some aspects, at transmitting RLC UM entity 1006, upon transmitting aplurality of consecutive RLC UM PDUs corresponding to a total number ofavailable RLC SN numbers, an RLC SN cycle is completed, transmitter RLCUM SN 1010 wraps around, and transmitter HFN 1012 is incremented. Forexample, in one aspect of an HSPA use case, the plurality of consecutiveRLC UM PDUs corresponding to a total number of available RLC SN numbersis 127 consecutive RLC UM PDUs. Meanwhile, if receiving RLC UM 1018entity misses more than the total number of available RLC SN numbers,e.g. more than 127 consecutive PDUs in the HSPA example, becausereceiving RLC UM entity 1018 is not aware of the missed consecutivePDUs, receiver HFN 1020 is not incremented, resulting in ade-synchronization between transmitter HFN 1012 and receiver HFN 1020.Thereafter, if further RLC UM PDUs are transmitted and receivedcorrectly, due to the de-synchronization between transmitter HFN 1012and receiver HFN 1020, the data in the received RLC UM PDUs will beerroneously deciphered at receiving RLC UM entity 1018.

Although the communication between a sender and a receiver in RLC UM isan un-acknowledged operation, the 3GPP standard provides a mechanism ofinter-layer communication within the transmitting RLC UM entity 1006 tolearn about the success or failure of the transmitted packets. Forexample, in 25.321 MAC specifications, there is a provision to indicatethe status of every PDU transmission by using primitives. A primitivehas an order or data form and is used for exchanging transmission orreception information between an upper layer and a lower layer. Table 1shows one non-limiting arrangement of primitives between a MAC layer andan RLC layer, although other arrangements may also be possible.

TABLE 1 An example of primitives between MAC and RLC Generic ParameterName Request Indication Response Confirm MAC_DATA Data, BO, Data, No_TB,UE-ID type TD (only in indicator, TDD), Error RLC entity indication infoMAC_STATUS No_PDU, BO, PDU_Size, RLC entity TX status info

As shown in Table 1, each logical channel and transport channel mayexchange a MAC_DATA primitive and a MAC_STATUS primitive between a MACsub-layer and an RLC sub-layer. As shown under the parameter header inTable 1, the primitives may provide a request, an indication, aresponse, a confirm, etc., between an upper layer and a lower layer. Forexample, a MAC_DATA_IND primitive may be used when data in a currentbuffer of a selected logical channel is required to be transmitted afterthe MAC transport format combination (TFC) selection process isperformed. The logical channel may transmit PDUs to the transportchannel using a MAC_DATA_REQ primitive according to a request. AMAC_STATUS_IND primitive may be used so that the transport channelinforms each logical channel of a size and a number of PDUstransmittable in the logical channel.

According to some aspects, a transmit (TX) status primitive may be usedby the MAC sub-layer to indicate the status of every PDU transmission tothe RLC sub-layer. For example, TX status may be set to a value of“transmission unsuccessful” to indicate to the RLC that the transmissionof an RLC PDU has failed in the previous transmission time interval(TTI). The TX status may also be set to a value of “transmissionsuccessful” to indicate to the RLC that a requested RLC PDU has beensubmitted for transmission by the physical layer. In some aspects, atransmission status of a PDU may be obtained from a protocol sub-layerdifferent than the MAC sub-layer.

Generally, in some aspects, ciphering may be performed in the RLCsub-layer when a radio bearer is using RLC UM. In these aspects,ciphering errors may be related to the ciphering sequence number COUNT-Cthat is a 32 bit ciphering parameter. There is one COUNT-C value perup-link radio bearer and one COUNT-C value per downlink radio bearerusing RLC UM. Table 2 shows a COUNT-C configuration in RLC UM.

TABLE 2 COUNT-C configuration in RLC UM HFN (25 bits) RLC UM SN (7 bits)

As shown in Table 2, COUNT-C in RLC UM is composed of two parts: a“short” sequence number and a “long” sequence number. The “short”sequence number forms the least significant bits of COUNT-C and is the7-bit RLC UM SN that is part of the RLC UM PDU header. The “long”sequence number forms the most significant bits of COUNT-C and is the25-bit RLC UM HFN that is incremented at each RLC SN cycle. The HFN maybe initialized by the parameter START, e.g., a wireless transmit/receiveunit (WTRU) and the radio network controller (RNC) may initialize themost significant bits of the RLC UM HFN to START, and the remaining bitsof the RLC UM HFN may be initialized to zero. The HFN may not beexplicitly transmitted with the packet.

Additionally, in an aspect, transmitting RLC UM entity 1002 furtherincludes MAC entity 1014 that performs the functions of the MACsub-layer. For every TTI, the MAC entity 1014 may request the pluralityof PDUs to be transmitted from each logical channel, based on variousfactors (such as buffer occupancy, priority, available power, availablegrant, etc.) on the current hybrid automatic repeat request (HARQ) thatis received by HARQ entity 1016. MAC entity 1014 may have the knowledgeof the transmission status of HARQ entity 1016 based on the peerfeedback (ACK/NAK) received by HARQ entity 1016. In some aspects,transmitting RLC UM entity 1006 may obtain the successful/unsuccessfultransmission status of each PDU from MAC entity 1014 based on thetransmission status of HARQ entity 1016. Accordingly, the transmittingRLC UM entity 1006 may store a history of PDU transmission status 1008and may include HFN de-synchronization condition determining component1024 that sets an HFN de-synchronization condition 1022 to be TRUEwhenever the history of PDU transmission status 1008 indicates that aplurality of consecutive PDUs are lost, e.g., 128 consecutive PDUs arelost. The HFN de-synchronization condition 1022 may be set to FALSEwhenever the history of PDU transmission status 1008 indicates that atleast one PDU out of such plurality of PDUs is successfully transmitted,e.g., at least one PDU out of the last 128 PDUs is successfullytransmitted. In some aspects, for example, HFN de-synchronizationcondition determining component 1024 may include transmission statusdetermining component 1028 that determines the successful/unsuccessfultransmission status of each PDU based on the transmission status of HARQentity 1016.

In some aspects, transmitting RLC UM entity 1006 and/or HFNde-synchronization condition determining component 1024 may determinethe value of HFN de-synchronization that resulted in a TRUE HFNde-synchronization condition 1022. To determine the value of HFNde-synchronization, an inter-layer communication may be used between MACentity 1014 and transmitting RLC UM entity 1006. For example, MAC entity1014 may provide the HARQ operation result for each HARQ transmissionand may also provide “fail/success” feedback to transmitter RLC UMentity 1006 via an inter-layer communication interface within firstcommunications apparatus 1002. Transmitting RLC UM entity 1006 may thenkeep track of the mapping of each HARQ fail/success with a correspondingtransmitter RLC UM SN 1010. For example, in one aspect, HFNde-synchronization condition determining component 1024 may includetransmission status mapping component 1030 that keeps track of themapping of each HARQ fail/success with a corresponding transmitter RLCUM SN 1010. According to one example, transmitting RLC UM entity 1006,HFN de-synchronization condition determining component 1024, and/ortransmission status mapping component 1030 may maintain an array of bitmaps that records the fail/success related to at least the most recent128 RLC UM PDU SNs, based on each MAC HARQ (re)transmission result(e.g., fail/success). In some aspects, transmitting RLC UM entity 1006,HFN de-synchronization condition determining component 1024, and/ortransmission status mapping component 1030 may keep track of thismapping regardless of whether the RLC PDU size is configured to be“fixed size” or “flexible size”. In these aspects, the PDU mappingbetween the two layers (e.g., MAC and RLC) may be done for both fixedand flexible RLC PDU sizes, subject to RLC PDU size configuration. Insome aspects, where the mapping between the logical channel and thephysical channels (e.g., the over the air radio channels) may beconfigured by the network, transmitter RLC UM entity 1006, HFNde-synchronization condition determining component 1024, and/ortransmission status mapping component 1030 may additionally oralternatively keep track of the PDU mapping regardless of how thelogical channels are multiplexed for over-the-air transmission.

In some aspects, first communications apparatus 1002 may be a UE or amobile device that transmits uplink packets to second communicationsapparatus 1004, which may be a network entity such as a base station ora Node B. In these aspects, as the MAC and RLC are co-located in themobile device, the inter-layer communication/signaling can be donethrough the implementation of primitives such as the TX status primitiveas described herein.

In some aspects, first communications apparatus 1002 may be a networkentity that transmits downlink packets to second communicationsapparatus 1004 which may be a UE or a mobile device. In these aspects,the inter-layer communication between the MAC and RLC layers may be viaan interface or signaling between a Node-B (where MAC entity 1014 andHARQ entity 1016 are located) and the RNC (where the transmitting RLC UMentity 1002 is located). This interface or signaling can be anenhancement of the existing Iu interface (e.g., the external interfacethat connects the RNC to the core network). This interface or signalingmay provide the MAC/HARQ “fail/success” feedback from the Node-B to theRNC, so that the transmitting RLC UM entity 1006 in RNC can determinethe HFN de-synchronization condition 1022 as described herein.

In some aspects, when HFN de-synchronization condition 1022 isdetermined to be TRUE, transmitter HFN 1012 may be adjusted, forexample, decremented, by the transmitting RLC UM entity 1006 and/or HFNadjusting component 1026, to ensure that transmitter HFN 1012 issynchronized with receiver HFN 1020, and that transmitting RLC UM entity1006 and receiving RLC UM entity 1018 are using the same HFN in COUNT-Cfor ciphering/deciphering.

The following is one example showing how the transmitter HFN 1012 can beadjusted by the transmitting RLC UM entity 1006 and/or HFN adjustingcomponent 1026. Assume that the transmitter HFN 1012 and the receiverHFN 1020 are both equal to 1, and transmitting RLC UM entity 1006 andreceiving RLC UM entity 1018 successfully exchange RLC PDU SN 0 to 25.Also assume that the transmitting RLC UM entity 1006 follows bytransmitting RLC UM PDU SN 26 to 127 using HFN 1, at which time thetransmitter RLC UM SN 1010 rolls over to 0, and assume further that RLCUM PDU SN 26 to 127 fail transmission (102 failed PDUs), e.g., anegative acknowledgement (NACK) is received by HARQ entity 1016 forthese transmissions. This NACK information can be extracted based onHARQ ACK/NACK status at HARQ entity 1016, and can be transmitted fromMAC entity 1014 to transmitting RLC UM entity 1006. When transmitter RLCUM SN 1010 re-starts at 0 (or rolls over), transmitter HFN 1012 isincremented to 2. Now assume that with this re-started RLC UM SN 1010,another RLC UM PDU SN 0 to 25 are transmitted using HFN 2 but failtransmission (26 failed PDUs). Accordingly, a total of 128 successivePDUs have failed transmission. In this situation, in the absence of thedetection of HFN de-synchronization, the transmitting RLC UM entity 1006uses HFN 2 while the receiving RLC UM entity 1018 uses HFN 1, resultingin HFN de-synchronization and leading to voice garbling for voice overHSPA applications. However, if the HFN de-synchronization is detected asTRUE based on the indication that 128 successive PDUs have failedtransmission, transmitter HFN 1012 may be adjusted (e.g., decremented)and HFN 1 may be used for the new PDUs to be transmitted. Meanwhile, atthe receiving RLC UM entity 1018, the receiver HFN 1020 remains equal to1 because none of the last 128 RLC UM PDUs were received, and receiverRLC UM SN 1024 did not roll over. Consequently, both the transmitter andthe receiver are using the same HFN 1, and the COUNT-C parameter is thesame ensuring synchronization of the ciphering/deciphering parameters.

In some aspect, a size of the plurality of consecutive PDUs used fordetermining HFN de-synchronization condition 1022 (e.g., the number ofPDUs within the plurality of PDUs) may be equal to or more than one fullRLC SN cycle. In one aspect, for example, the size of the plurality ofconsecutive PDUs used for determining HFN de-synchronization condition1022 may be a multiple of one full RLC SN cycle. In this aspect,transmitter HFN 1012 may be adjusted according to the multiple of onefull RLC SN cycle. For example, if the multiple of one full RLC SN cycleis 3 RLC SN full cycles, then, upon a determination of a TRUE HFNde-synchronization condition 1022, transmitter HFN 1012 may besubtracted by 3 at transmitting RLC UM entity 1006 to re-sync HFN.According to one example, the length of one full RLC SN cycle is 128.

Referring to FIG. 2, in one aspect, a method 2000 for managing HFNde-synchronization in RLC UM is illustrated. According to one or moreaspects of method 2000, a transmitter may detect HFN de-synchronizationand take corrective action even when the transmitter is operating in RLCUM. For explanatory purposes, method 2000 will be discussed withreference to the above described FIG. 1. It should be understood that inother implementations, other systems and/or communications apparatus,UEs, Node Bs, or other apparatus comprising different components thanthose illustrated in FIG. 1 may be used in implementing method 2000 ofFIG. 2.

At block 2002, method 2000 includes determining an HFNde-synchronization condition that is FALSE when at least one PDU out ofa plurality of successive PDUs is successfully transmitted, and that isTRUE when all of the plurality of successive PDUs are lost. For example,in an aspect, first communications apparatus 1002 and/or HFNde-synchronization condition determining component 1024 may determineHFN de-synchronization condition 1022 based on the history of PDUtransmission status 1008 obtained from HARQ entity 1016. HFNde-synchronization condition 1022 may be set to TRUE when all of theplurality of successive PDUs (for example, 128 successive PDUs) arelost, and may be set to FALSE when at least one PDU out of a pluralityof successive PDUs is successfully transmitted. According to someaspects, a TX status primitive may be used by the MAC sub-layer toindicate the status of every PDU transmission to the RLC sub-layer.

For example, in an aspect of execution of block 2002, in every TTI, aMAC entity may request the plurality of PDUs to be transmitted from eachlogical channel based on various factors (e.g., buffer occupancy,priority, available power, available grant, etc.) on the current HARQ.In some aspects, the MAC entity may also know a HARQ entity transmissionstatus based on peer feedback (e.g., ACK/NAK). In some aspects, forexample, the RLC entity may get the successful/unsuccessful transmissionstatus of each PDU based on the HARQ status from the MAC entity.Accordingly, in these aspects, HFN de-synchronization may be set to TRUEwhen a loss of a plurality of consecutive PDUs (e.g., 128 consecutivePDUs) is identified by the transmitter. Also, HFN de-synchronization maybe set to FALSE when at least one PDU out of the last plurality ofconsecutive PDUs (e.g., the last 128 consecutive PDUs) is identified tobe successfully transmitted.

In some aspects, an RLC UM transmitter may use the inter-layercommunication between two protocol layers (e.g., MAC sub-layer and RLCsub-layer), so that the MAC sub-layer can provide to the RLC sub-layer aHARQ operation result of a HARQ transmission. As such, in these aspects,within the transmitter itself, the MAC sub-layer provides thefail/success feedback to the RLC UM entity via an inter-layercommunication interface. In some aspects, the RLC sub-layer keeps trackof the mapping of a HARQ fail/success with a corresponding RLC UM SN. Inone aspect, for example, the RLC UM entity may maintain an array of bitmap that records the fail/success of, at least, a number of the mostrecent RLC UM PDU sequence numbers (e.g., at least the 128 most recentRLC UM PDU sequence numbers), based on each MAC HARQ transmission orretransmission result (e.g., fail or success). In some aspects, the RLCsub-layer may keep track of the mapping of the HARQ fail/success withthe corresponding RLC UM SN, regardless of whether an RLC PDU size isconfigured to be flexible or fixed. In some aspect, alternatively oradditionally, the RLC sub-layer may keep track of the HARQ fail/successmapping regardless of how the logical channels are multiplexed fortransmission over the air.

In some aspects, when the transmitter is transmitting a downlinkcommunication (e.g., transmitting from a network to a mobile device), anetwork inter-layer communication may be performed by an interface orsignaling from, e.g., a Node-B where MAC/HARQ function is located, to,e.g., the RNC (radio network controller) where an RLC UM transmitter islocated. In these aspects, such interface may, for example, be a part ofan existing Iu interface with enhancement, and may provide the MAC/HARQfail/success feedback from the Node-B to the RNC, so that the RLC UMentity in the RNC can determine the HFN de-synchronization condition.

In some aspects, when the transmitter is transmitting an uplinkcommunication (e.g., when the transmitter is a mobile device), since theMAC and RLC are co-located in the transmitter (e.g., mobile device), aninter-layer communication/signaling may be performed for the bit-maptracking as described herein.

At block 2004, method 2000 includes adjusting a transmitter HFN when theHFN de-synchronization condition is TRUE. As such, the RLC UMtransmitter may update a transmitter HFN to ensure ciphering parametersynchronization, when the HFN de-synchronization condition is TRUE. Forexample, in an aspect, HFN adjusting component 1026 may adjusttransmitter HFN 1012 when HFN de-synchronization condition is TRUE.

For example, in some aspects of an execution of block 2004, when an HFNde-synchronization is detected, a transmitter HFN may be decremented bythe RLC UM transmitter to ensure that both peer entities are using thesame HFN in COUNT-C for ciphering/deciphering. The following is onenon-limiting example of how the HFN can be adjusted by the RLC UMtransmitter. In this example, in step a, a transmitter and a receiverexchange RLC UM PDU SN 0 to 25 with HFN 1. Then, in step b, RLC UM PDUSN 26 to SN 127 are transmitted using HFN 1. At this time the SN is tobe rolled over to 0. In step c, on SN rollover, HFN is incremented to 2,and RLC UM PDU SN 0 to SN 25 are transmitted using HFN 2 (e.g., SNre-starts or rolls over from 0, and HFN is increased by 1, according tothe standard protocol). In step d of this example, all the PDUs in stepsb and c (128 PDUs consecutively) are failed transmissions (e.g., thereceiver has NAKed all those transitions via HARQ operation), and “HFNDe-synchronization” is detected. This NAK information can be extractedbased on HARQ ACK/NAK status from MAC to RLC. Without any HFNadjustment, at this stage of this example, the transmitter is using HFN2 while the receiver is using HFN 1, which results in HFNde-synchronization and can lead to voice garbling issues for voice overHSPA applications. However, by detecting the “HFN De-synchronization” asTRUE, in step e, HFN is decremented at the transmitter side, and HFN 1is used for the new PDUs to be transmitted. Meanwhile, at the receiverside, HFN is kept as 1 because none of the last 128 RLC UM PDUs werereceived and RLC UM SN did not roll over. As a result, both thetransmitter and the receiver are using the same HFN, and COUNT-Cparameter is the same, ensuring synchronization of the cipher/decipherparameters. The error detection based on 128 consecutive PDUs is justone example without loss of generality, and the error detection may beextended for any multiple of 128 consecutive PDUs as the detectioncycle, and the HFN can be adjusted accordingly at the RLC UM transmitterto re-synchronize HFN.

Thus, the present apparatus and methods determine a condition of HFNde-synchronization at a transmitter RLC UM entity, and when suchcondition is determined to be TRUE, the present apparatus and methodsperform an HFN update at the transmitter.

FIG. 3 is a block diagram illustrating an example of a hardwareimplementation for an apparatus 100 employing a processing system 114 tooperate, for example, first communications apparatus 1002, secondcommunications apparatus 1004, transmitting RLC UM entity 1006, MACentity 1014, receiving RLC UM entity 1018, and/or respective componentsthereof (see FIG. 1). For example, in one aspect, apparatus 100 mayoperate first communications apparatus 1002 and may include RLC/MAC UMentity 116 and MAC entity 118, which may be the same as or similar totransmitting RLC UM entity 1006 and MAC entity 1014, respectively. Inanother aspect, for example, apparatus 100 may operate secondcommunications apparatus 1004 and may include RLC/MAC UM entity 116,which may be the same as or similar to receiving RLC UM entity 1018. Inaccordance with various aspects of the disclosure, an element, or anyportion of an element, or any combination of elements may be implementedwith a processing system 114 that includes one or more processors 104.Examples of processors 104 include microprocessors, microcontrollers,digital signal processors (DSPs), field programmable gate arrays(FPGAs), programmable logic devices (PLDs), state machines, gated logic,discrete hardware circuits, and other suitable hardware configured toperform the various functionality described throughout this disclosure.

In this example, the processing system 114 may be implemented with a busarchitecture, represented generally by the bus 102. The bus 102 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 114 and the overall designconstraints. The bus 102 links together various circuits including oneor more processors (represented generally by the processor 104), amemory 105, and computer-readable media (represented generally by thecomputer-readable medium 106). The bus 102 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further. A bus interface 108provides an interface between the bus 102 and a transceiver 110. Thetransceiver 110 provides a means for communicating with various otherapparatus over a transmission medium. Depending upon the nature of theapparatus, a user interface 112 (e.g., keypad, display, speaker,microphone, joystick) may also be provided.

The processor 104 is responsible for managing the bus 102 and generalprocessing, including the execution of software stored on thecomputer-readable medium 106. The software, when executed by theprocessor 104, causes the processing system 114 to perform the variousfunctions described infra for any particular apparatus. Thecomputer-readable medium 106 may also be used for storing data that ismanipulated by the processor 104 when executing software. Alternativelyor additionally, apparatus 100 may include RLC/MAC UM entity 116 and MACentity 118 such that, when executed by the processor 104, RLC/MAC UMentity 116 and MAC entity 118 perform the various functions describedinfra for a respective one of first communications apparatus 1002,second communications apparatus 1004, transmitting RLC UM entity 1006,MAC entity 1014, or receiving RLC UM entity 1018 (see FIG. 1).

One or more processors 104 in the processing system may executesoftware. Software shall be construed broadly to mean instructions,instruction sets, code, code segments, program code, programs,subprograms, software modules, applications, software applications,software packages, routines, subroutines, objects, executables, threadsof execution, procedures, functions, etc., whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. The software may reside on a computer-readablemedium 106. The computer-readable medium 106 may be a non-transitorycomputer-readable medium. A non-transitory computer-readable mediumincludes, by way of example, a magnetic storage device (e.g., hard disk,floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD)or a digital versatile disc (DVD)), a smart card, a flash memory device(e.g., a card, a stick, or a key drive), a random access memory (RAM), aread only memory (ROM), a programmable ROM (PROM), an erasable PROM(EPROM), an electrically erasable PROM (EEPROM), a register, a removabledisk, and any other suitable medium for storing software and/orinstructions that may be accessed and read by a computer. Thecomputer-readable medium may also include, by way of example, a carrierwave, a transmission line, and any other suitable medium fortransmitting software and/or instructions that may be accessed and readby a computer. The computer-readable medium 106 may reside in theprocessing system 114, external to the processing system 114, ordistributed across multiple entities including the processing system114. The computer-readable medium 106 may be embodied in a computerprogram product. By way of example, a computer program product mayinclude a computer-readable medium in packaging materials. Those skilledin the art will recognize how best to implement the describedfunctionality presented throughout this disclosure depending on theparticular application and the overall design constraints imposed on theoverall system.

The various concepts presented throughout this disclosure may beimplemented across a broad variety of telecommunication systems, networkarchitectures, and communication standards. Referring now to FIG. 4, asan illustrative example without limitation, various aspects of thepresent disclosure are illustrated with reference to a Universal MobileTelecommunications System (UMTS) system 200. A UMTS network includesthree interacting domains: a core network 204, a radio access network(RAN) (e.g., the UMTS Terrestrial Radio Access Network (UTRAN) 202), anda user equipment (UE) 210. Any transmitting and receiving pair ofdevices, e.g., UE 210 and UTRAN 202, may respectively include or besimilar to first communications apparatus 1002 and second communicationsapparatus 1004, and/or their respective components, e.g., transmittingRLC UM entity 1006, MAC entity 1014, receiving RLC UM entity 1018,apparatus 100, and/or any other components thereof (see FIGS. 1 and 3).

Among several options available for a UTRAN 202, in this example, theillustrated UTRAN 202 may employ a W-CDMA air interface for enablingvarious wireless services including telephony, video, data, messaging,broadcasts, and/or other services. The UTRAN 202 may include a pluralityof Radio Network Subsystems (RNSs) such as an RNS 207, each controlledby a respective Radio Network Controller (RNC) such as an RNC 206. Here,the UTRAN 202 may include any number of RNCs 206 and RNSs 207 inaddition to the illustrated RNCs 206 and RNSs 207. The RNC 206 is anapparatus responsible for, among other things, assigning, reconfiguring,and releasing radio resources within the RNS 207. The RNC 206 may beinterconnected to other RNCs (not shown) in the UTRAN 202 throughvarious types of interfaces such as a direct physical connection, avirtual network, or the like using any suitable transport network.

The geographic region covered by the RNS 207 may be divided into anumber of cells, with a radio transceiver apparatus serving each cell. Aradio transceiver apparatus is commonly referred to as a Node B in UMTSapplications, but may also be referred to by those skilled in the art asa base station (BS), a base transceiver station (BTS), a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), an access point (AP), or someother suitable terminology. For clarity, three Node Bs 208 are shown ineach RNS 207; however, the RNSs 207 may include any number of wirelessNode Bs. The Node Bs 208 provide wireless access points to a corenetwork 204 for any number of mobile apparatuses. Examples of a mobileapparatus include a cellular phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, apersonal digital assistant (PDA), a satellite radio, a globalpositioning system (GPS) device, a multimedia device, a video device, adigital audio player (e.g., MP3 player), a camera, a game console, orany other similar functioning device. The mobile apparatus is commonlyreferred to as user equipment (UE) in UMTS applications, but may also bereferred to by those skilled in the art as a mobile station (MS), asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal (AT), a mobile terminal, a wireless terminal, a remoteterminal, a handset, a terminal, a user agent, a mobile client, aclient, or some other suitable terminology. In a UMTS system, the UE 210may further include a universal subscriber identity module (USIM) 211,which contains a user's subscription information to a network. Forillustrative purposes, one UE 210 is shown in communication with anumber of the Node Bs 208. The downlink (DL), also called the forwardlink, refers to the communication link from a Node B 208 to a UE 210 andthe uplink (UL), also called the reverse link, refers to thecommunication link from a UE 210 to a Node B 208.

The core network 204 can interface with one or more access networks,such as the UTRAN 202. As shown, the core network 204 is a UMTS corenetwork. However, as those skilled in the art will recognize, thevarious concepts presented throughout this disclosure may be implementedin a RAN, or other suitable access network, to provide UEs with accessto types of core networks other than UMTS networks.

The illustrated UMTS core network 204 includes a circuit-switched (CS)domain and a packet-switched (PS) domain. Some of the circuit-switchedelements are a Mobile services Switching Centre (MSC), a VisitorLocation Register (VLR), and a Gateway MSC (GMSC). Packet-switchedelements include a Serving GPRS Support Node (SGSN) and a Gateway GPRSSupport Node (GGSN). Some network elements, like EIR, HLR, VLR, and AuCmay be shared by both of the circuit-switched and packet-switcheddomains.

In the illustrated example, the core network 204 supportscircuit-switched services with a MSC 212 and a GMSC 214. In someapplications, the GMSC 214 may be referred to as a media gateway (MGW).One or more RNCs, such as the RNC 206, may be connected to the MSC 212.The MSC 212 is an apparatus that controls call setup, call routing, andUE mobility functions. The MSC 212 also includes a visitor locationregister (VLR) that contains subscriber-related information for theduration that a UE is in the coverage area of the MSC 212. The GMSC 214provides a gateway through the MSC 212 for the UE to access acircuit-switched network 216. The GMSC 214 includes a home locationregister (HLR) 215 containing subscriber data, such as the datareflecting the details of the services to which a particular user hassubscribed. The HLR is also associated with an authentication center(AuC) that contains subscriber-specific authentication data. When a callis received for a particular UE, the GMSC 214 queries the HLR 215 todetermine the UE's location and forwards the call to the particular MSCserving that location.

The illustrated core network 204 also supports packet-switched dataservices with a serving GPRS support node (SGSN) 218 and a gateway GPRSsupport node (GGSN) 220. General Packet Radio Service (GPRS) is designedto provide packet-data services at speeds higher than those availablewith standard circuit-switched data services. The GGSN 220 provides aconnection for the UTRAN 202 to a packet-based network 222. Thepacket-based network 222 may be the Internet, a private data network, orsome other suitable packet-based network. The primary function of theGGSN 220 is to provide the UEs 210 with packet-based networkconnectivity. Data packets may be transferred between the GGSN 220 andthe UEs 210 through the SGSN 218, which performs primarily the samefunctions in the packet-based domain as the MSC 212 performs in thecircuit-switched domain.

The UTRAN air interface may be a spread spectrum Direct-Sequence CodeDivision Multiple Access (DS-CDMA) system, such as one utilizing theW-CDMA standards. The spread spectrum DS-CDMA spreads user data throughmultiplication by a sequence of pseudorandom bits called chips. TheW-CDMA air interface for the UTRAN 202 is based on such DS-CDMAtechnology and additionally calls for a frequency division duplexing(FDD). FDD uses a different carrier frequency for the uplink (UL) anddownlink (DL) between a Node B 208 and a UE 210. Another air interfacefor UMTS that utilizes DS-CDMA, and uses time division duplexing (TDD),is the TD-SCDMA air interface. Those skilled in the art will recognizethat although various examples described herein may refer to a W-CDMAair interface, the underlying principles are equally applicable to aTD-SCDMA air interface or any other suitable air interface.

In a wireless telecommunication system, the communication protocolarchitecture may take on various forms depending on the particularapplication. For example, in a 3GPP UMTS system, the signaling protocolstack is divided into a Non-Access Stratum (NAS) and an Access Stratum(AS). The NAS provides the upper layers, for signaling between the UE210 and the core network 204 (referring to FIG. 2), and may includecircuit switched and packet switched protocols. The AS provides thelower layers, for signaling between the UTRAN 202 and the UE 210, andmay include a user plane and a control plane. Here, the user plane ordata plane carries user traffic, while the control plane carries controlinformation (i.e., signaling).

Turning to FIG. 5, the access stratum (AS) is shown with three layers L1316, L2 308, and L3 318, in an example radio protocol architecture 300relating to the user plane 302 and the control plane 304 of a userequipment (UE) or a node B/base station. For example, architecture 300may be included in first communications apparatus 1002, secondcommunications apparatus 1004, or apparatus 100 (see FIGS. 1 and 3), orin UE 210 or Node B 208 (see FIG. 4).

Layer 1 316 is the lowest layer and implements various physical layersignal processing functions. Layer 1 316 will be referred to herein asthe physical layer 306. The data link layer, called Layer 2 308, isabove the physical layer 306 and is responsible for the link between theUE 210 and Node B 208 over the physical layer 306.

At Layer 3, the RRC layer 316 handles the control plane signalingbetween the UE 210 and the Node B 208. RRC layer 316 includes a numberof functional entities for routing higher layer messages, handlingbroadcasting and paging functions, establishing and configuring radiobearers, etc.

In the illustrated air interface, the L2 layer 308 is split intosublayers. In the control plane, the L2 layer 308 includes twosublayers: a media access control (MAC) sublayer 310 and a radio linkcontrol (RLC) sublayer 312. In the user plane, the L2 layer 308additionally includes a packet data convergence protocol (PDCP) sublayer314. Although not shown, the UE may have several upper layers above theL2 layer 308 including a network layer (e.g., IP layer) that isterminated at a PDN gateway on the network side and an application layerthat is terminated at the other end of the connection (e.g., far end UE,server, etc.).

The PDCP sublayer 314 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 314 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between Node Bs.

The RLC sublayer 312 generally supports an acknowledged mode (AM) (wherean acknowledgment and retransmission process may be used for errorcorrection), an unacknowledged mode (UM), and a transparent mode fordata transfers, and provides segmentation and reassembly of upper layerdata packets and reordering of data packets to compensate forout-of-order reception due to a hybrid automatic repeat request (HARQ)at the MAC layer. In the acknowledged mode, RLC peer entities such as anRNC and a UE may exchange various RLC protocol data units (PDUs)including RLC Data PDUs, RLC Status PDUs, and RLC Reset PDUs, amongothers. In the present disclosure, the term “packet” may refer to anyRLC PDU exchanged between RLC peer entities.

The MAC sublayer 310 provides multiplexing between logical and transportchannels. The MAC sublayer 310 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 310 is also responsible for HARQ operations.

The MAC sublayer 310 includes various MAC entities, including but notlimited to a MAC-d entity and a MAC-hs/ehs entity. The Radio NetworkController (RNC) houses protocol layers from MAC-d and above. For thehigh speed channels, the MAC-hs/ehs layer is housed in the Node B.

From the UE side, The MAC-d entity is configured to control access toall the dedicated transport channels, to a MAC-c/sh/m entity, and to theMAC-hs/ehs entity. Further, from the UE side, the MAC-hs/ehs entity isconfigured to handle the HSDPA specific functions and control access tothe HS-DSCH transport channel. Upper layers configure which of the twoentities, MAC-hs or MAC-ehs, is to be applied to handle HS-DSCHfunctionality.

Referring to FIG. 6, an access network 300 in a UTRAN architecture isillustrated in which one or more of the wireless communication entities,e.g., UEs and/or base stations, may include, for example, firstcommunications apparatus 1002, second communications apparatus 1004, UE210, Node B 208, transmitting RLC UM entity 1006, MAC entity 1014,receiving RLC UM entity 1018, or apparatus 100 (see FIGS. 1, 3, and 4).

The system includes multiple cellular regions (cells), including cells302, 304, and 306, each of which may include one or more sectors. Cellsmay be defined geographically (e.g., by coverage area) and/or may bedefined in accordance with a frequency, scrambling code, etc. That is,the illustrated geographically-defined cells 302, 304, and 306 may eachbe further divided into a plurality of cells, e.g., by utilizingdifferent scrambling codes. For example, cell 304 a may utilize a firstscrambling code, and cell 304 b, while in the same geographic region andserved by the same Node B 344, may be distinguished by utilizing asecond scrambling code.

In a cell that is divided into sectors, the multiple sectors within acell can be formed by groups of antennas with each antenna responsiblefor communication with UEs in a portion of the cell. For example, incell 302, antenna groups 312, 314, and 316 may each correspond to adifferent sector. In cell 304, antenna groups 318, 320, and 322 may eachcorrespond to a different sector. In cell 306, antenna groups 324, 326,and 328 may each correspond to a different sector.

The cells 302, 304, and 306 may include several UEs that may be incommunication with one or more sectors of each cell 302, 304, or 306.For example, UEs 330 and 332 may be in communication with Node B 342,UEs 334 and 336 may be in communication with Node B 344, and UEs 338 and340 may be in communication with Node B 346. Here, each Node B 342, 344,and 346 may be configured to provide an access point to a core network204 (see FIG. 4) for all the UEs 330, 332, 334, 336, 338, and 340 in therespective cells 302, 304, and 306.

During a call with a source cell, or at any other time, the UE 336 maymonitor various parameters of the source cell as well as variousparameters of neighboring cells. Further, depending on the quality ofthese parameters, the UE 336 may maintain communication with one or moreof the neighboring cells. During this time, the UE 336 may maintain anActive Set, that is, a list of cells to which the UE 336 issimultaneously connected (i.e., the UTRAN cells that are currentlyassigning a downlink dedicated physical channel DPCH or fractionaldownlink dedicated physical channel F-DPCH to the UE 336 may constitutethe Active Set).

FIG. 7 is a block diagram of a telecommunications system 700 comprisinga Node B 710 in communication with a UE 750, where the Node B 710 andthe UE 750 may include first communications apparatus 1002, secondcommunications apparatus 1004, UE 210, Node B 208, transmitting RLC UMentity 1006, receiving RLC UM entity 1018, MAC entity 1014, or apparatus100 (see FIGS. 1, 3, and 4).

In the downlink communication, a transmit processor 720 may receive datafrom a data source 712 and control signals from a controller/processor740. The transmit processor 720 provides various signal processingfunctions for the data and control signals, as well as reference signals(e.g., pilot signals). For example, the transmit processor 720 mayprovide cyclic redundancy check (CRC) codes for error detection, codingand interleaving to facilitate forward error correction (FEC), mappingto signal constellations based on various modulation schemes (e.g.,binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM),and the like), spreading with orthogonal variable spreading factors(OVSF), and multiplying with scrambling codes to produce a series ofsymbols. Channel estimates from a channel processor 744 may be used by acontroller/processor 740 to determine the coding, modulation, spreading,and/or scrambling schemes for the transmit processor 720. These channelestimates may be derived from a reference signal transmitted by the UE750 or from feedback from the UE 750. The symbols generated by thetransmit processor 720 are provided to a transmit frame processor 730 tocreate a frame structure. The transmit frame processor 730 creates thisframe structure by multiplexing the symbols with information from thecontroller/processor 740, resulting in a series of frames. The framesare then provided to a transmitter 732, which provides various signalconditioning functions including amplifying, filtering, and modulatingthe frames onto a carrier for downlink transmission over the wirelessmedium through antenna 734. The antenna 734 may include one or moreantennas, for example, including beam steering bidirectional adaptiveantenna arrays or other similar beam technologies.

At the UE 750, a receiver 754 receives the downlink transmission throughan antenna 752 and processes the transmission to recover the informationmodulated onto the carrier. The information recovered by the receiver754 is provided to a receive frame processor 760, which parses eachframe, and provides information from the frames to a channel processor794 and the data, control, and reference signals to a receive processor770. The receive processor 770 then performs the inverse of theprocessing performed by the transmit processor 720 in the Node B 710.More specifically, the receive processor 770 descrambles and despreadsthe symbols, and then determines the most likely signal constellationpoints transmitted by the Node B 710 based on the modulation scheme.These soft decisions may be based on channel estimates computed by thechannel processor 794. The soft decisions are then decoded anddeinterleaved to recover the data, control, and reference signals. TheCRC codes are then checked to determine whether the frames weresuccessfully decoded. The data carried by the successfully decodedframes will then be provided to a data sink 772, which representsapplications running in the UE 750 and/or various user interfaces (e.g.,display). Control signals carried by successfully decoded frames will beprovided to a controller/processor 790. When frames are unsuccessfullydecoded by the receiver processor 770, the controller/processor 790 mayalso use an acknowledgement (ACK) and/or negative acknowledgement (NACK)protocol to support retransmission requests for those frames.

In the uplink, data from a data source 778 and control signals from thecontroller/processor 790 are provided to a transmit processor 780. Thedata source 778 may represent applications running in the UE 750 andvarious user interfaces (e.g., keyboard). Similar to the functionalitydescribed in connection with the downlink transmission by the Node B710, the transmit processor 780 provides various signal processingfunctions including CRC codes, coding and interleaving to facilitateFEC, mapping to signal constellations, spreading with OVSFs, andscrambling to produce a series of symbols. Channel estimates, derived bythe channel processor 794 from a reference signal transmitted by theNode B 710 or from feedback contained in the midamble transmitted by theNode B 710, may be used to select the appropriate coding, modulation,spreading, and/or scrambling schemes. The symbols produced by thetransmit processor 780 will be provided to a transmit frame processor782 to create a frame structure. The transmit frame processor 782creates this frame structure by multiplexing the symbols withinformation from the controller/processor 790, resulting in a series offrames. The frames are then provided to a transmitter 756, whichprovides various signal conditioning functions including amplification,filtering, and modulating the frames onto a carrier for uplinktransmission over the wireless medium through the antenna 752.

The uplink transmission is processed at the Node B 710 in a mannersimilar to that described in connection with the receiver function atthe UE 750. A receiver 735 receives the uplink transmission through theantenna 734 and processes the transmission to recover the informationmodulated onto the carrier. The information recovered by the receiver735 is provided to a receive frame processor 736, which parses eachframe, and provides information from the frames to the channel processor744 and the data, control, and reference signals to a receive processor738. The receive processor 738 performs the inverse of the processingperformed by the transmit processor 780 in the UE 750. The data andcontrol signals carried by the successfully decoded frames may then beprovided to a data sink 739 and the controller/processor, respectively.If some of the frames were unsuccessfully decoded by the receiveprocessor, the controller/processor 740 may also use an acknowledgement(ACK) and/or negative acknowledgement (NACK) protocol to supportretransmission requests for those frames.

The controller/processors 740 and 790 may be used to direct theoperation at the Node B 710 and the UE 750, respectively. For example,the controller/processors 740 and 790 may provide various functionsincluding timing, peripheral interfaces, voltage regulation, powermanagement, and other control functions. The computer readable media ofmemories 742 and 792 may store data and software for the Node B 710 andthe UE 750, respectively. A scheduler/processor 746 at the Node B 710may be used to allocate resources to the UEs and schedule downlinkand/or uplink transmissions for the UEs.

A high speed packet access (HSPA) air interface includes a series ofenhancements to the 3G/W-CDMA air interface between the UE 750 and theNode B 710, facilitating greater throughput and reduced latency forusers. Among other modifications over prior standards, HSPA utilizeshybrid automatic repeat request (HARM), shared channel transmission, andadaptive modulation and coding. The standards that define HSPA includeHSDPA (high speed downlink packet access) and HSUPA (high speed uplinkpacket access, also referred to as enhanced uplink or EUL).

For example, in Release 5 of the 3GPP family of standards, HSDPA wasintroduced. HSDPA utilizes as its transport channel the high-speeddownlink shared channel (HS-DSCH), which may be shared by several UEs.The HS-DSCH is implemented by three physical channels: the high-speedphysical downlink shared channel (HS-PDSCH), the high-speed sharedcontrol channel (HS-SCCH), and the high-speed dedicated physical controlchannel (HS-DPCCH).

The HS-SCCH is a physical channel that may be utilized to carry downlinkcontrol information related to the transmission of HS-DSCH. Here, theHS-DSCH may be associated with one or more HS-SCCH. The UE maycontinuously monitor the HS-SCCH to determine when to read its data fromthe HS-DSCH and to determine the modulation scheme used on the assignedphysical channel.

The HS-PDSCH is a physical channel that may be shared by several UEs andmay carry downlink data for the high-speed downlink. The HS-PDSCH maysupport quadrature phase shift keying (QPSK), 16-quadrature amplitudemodulation (16-QAM), and multi-code transmission.

The HS-DPCCH is an uplink physical channel that may carry feedback fromthe UE to assist the Node B in its scheduling algorithm. The feedbackmay include a channel quality indicator (CQI) and a positive or negativeacknowledgement (ACK/NAK) of a previous HS-DSCH transmission.

One difference on the downlink between Release-5 HSDPA and thepreviously standardized circuit-switched air-interface is the absence ofsoft handover in HSDPA. This means that HSDPA channels are transmittedto the UE from a single cell called the HSDPA serving cell. As the usermoves, or as one cell becomes preferable to another, the HSDPA servingcell may change. Still, the UE may be in soft handover on the associatedDPCH, receiving the same information from plural cells.

In Release 5 HSDPA, at any instance a UE 210 has one serving cell: thestrongest cell in the active set as according to the UE measurements ofE_(c)/I₀. According to mobility procedures defined in Release 5 of 3GPPTS 25.331, the radio resource control (RRC) signaling messages forchanging the HSPDA serving cell are transmitted from the current HSDPAserving cell (i.e., the source cell) and not the cell that the UEreports as being the stronger cell (i.e., the target cell).

3GPP Release 6 specifications introduced uplink enhancements referred toas Enhanced Uplink (EUL) or High Speed Uplink Packet Access (HSUPA).HSUPA utilizes as its transport channel the EUL Dedicated Channel(E-DCH). The E-DCH is transmitted in the uplink together with theRelease 99 DCH. The control portion of the DCH, that is, the DPCCH,carries pilot bits and downlink power control commands on uplinktransmissions.

The E-DCH is implemented by physical channels including the E-DCHDedicated Physical Data Channel (E-DPDCH) and the E-DCH DedicatedPhysical Control Channel (E-DPCCH). In addition, HSUPA relies onadditional physical channels including the E-DCH HARQ Indicator Channel(E-HICH), the E-DCH Absolute Grant Channel (E-AGCH), and the E-DCHRelative Grant Channel (E-RGCH).

Several aspects of a telecommunications system have been presented withreference to a W-CDMA system. As those skilled in the art will readilyappreciate, various aspects described throughout this disclosure may beextended to other telecommunication systems, network architectures andcommunication standards.

By way of example, various aspects may be extended to other UMTS systemssuch as TD-SCDMA and TD-CDMA. Various aspects may also be extended tosystems employing Long Term Evolution (LTE) (in FDD, TDD, or bothmodes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000,Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB),Bluetooth, and/or other suitable systems. The actual telecommunicationstandard, network architecture, and/or communication standard employedwill depend on the specific application and the overall designconstraints imposed on the system.

It is to be understood that the specific order or hierarchy of steps inthe methods disclosed is an illustration of exemplary processes. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the methods may be rearranged. The accompanyingmethod claims present elements of the various steps in a sample order,and are not meant to be limited to the specific order or hierarchypresented unless specifically recited therein.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, band c. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. §112, sixth paragraph,unless the element is expressly recited using the phrase “means for” or,in the case of a method claim, the element is recited using the phrase“step for.”

What is claimed is:
 1. A method of data communication between atransmitter and a receiver in a radio link control (RLC) unacknowledgedmode (UM), comprising: determining, by the transmitter operating in theRLC UM, a hyper frame number (HFN) de-synchronization condition, whereinthe HFN de-synchronization condition is FALSE when at least one protocoldata unit (PDU) out of a plurality of successive PDUs is successfullytransmitted by the transmitter to the receiver, wherein the HFNde-synchronization condition is TRUE when all of the plurality ofsuccessive PDUs are lost, and wherein a number of the plurality ofsuccessive PDUs is equal to a full cycle of RLC UM sequence numbers, amultiple of the full cycle of RLC UM sequence numbers, or a numbergreater than the full cycle of RLC UM sequence numbers; and adjusting,by the transmitter operating in the RLC UM, a transmitter HFN of thetransmitter in response to the HFN de-synchronization condition is TRUE,wherein the adjusted transmitter HFN is used for new PDUs to betransmitted in the RLC UM.
 2. The method of claim 1, wherein thedetermining comprises: determining, by an RLC sub-layer of thetransmitter, a successful or unsuccessful transmission status of a PDUbased on a transmission status of the PDU in a media access control(MAC) sub-layer; and mapping, by the RLC sub-layer, the successful orunsuccessful transmission status to the plurality of successive PDUs. 3.The method of claim 2, wherein the transmission status comprises ahybrid automatic repeat request (HARM), wherein the MAC sub-layerprovides a transmit status primitive to the RLC sub-layer, wherein thetransmit status primitive indicates a status of a PDU transmission. 4.The method of claim 2, wherein the data communication comprises anuplink communication from the transmitter to the receiver, wherein theMAC sub-layer and the RLC sub-layer are collocated at the transmitter,wherein the MAC sub-layer provides the HARQ to the RLC sub-layer via aninter-layer communication interface between the MAC sub-layer and theRLC sub-layer.
 5. The method of claim 2, wherein the data communicationcomprises a downlink communication from the transmitter to the receiver,wherein the MAC sub-layer provides the HARQ to the RLC sub-layer via anetwork inter-layer communication between a first network entity and asecond network entity, wherein the first network entity comprises theRLC sub-layer, and wherein the second network entity comprises the MACsub-layer.
 6. The method of claim 1, wherein each one of the transmitteror the receiver comprises a Node B, a user equipment, or a networkentity.
 7. The method of claim 1, wherein the adjusting the transmitterHFN comprises: adjusting the transmitter HFN to synchronize thetransmitter HFN with a receiver HFN of the receiver, wherein cipheringand deciphering parameters of the transmitter and the receiver aresynchronized when the transmitter and the receiver use a same HFN and asame RLC UM sequence number.
 8. The method of claim 1, wherein theadjusting of the transmitter HFN comprises: decrementing the transmitterHFN.
 9. A non-transitory computer-readable medium storingcomputer-executable code for data communication between a transmitterand a receiver in a radio link control (RLC) unacknowledged mode (UM),comprising: code for determining, by the transmitter operating in theRLC UM, a hyper frame number (HFN) de-synchronization condition, whereinthe HFN de-synchronization condition is FALSE when at least one protocoldata unit (PDU) out of a plurality of successive PDUs is successfullytransmitted by the transmitter to the receiver, wherein the HFNde-synchronization condition is TRUE when all of the plurality ofsuccessive PDUs are lost, and wherein a number of the plurality ofsuccessive PDUs is equal to a full cycle of RLC UM sequence numbers, amultiple of the full cycle of RLC UM sequence numbers, or a numbergreater than the full cycle of RLC UM sequence numbers; and code foradjusting, by the transmitter operating in the RLC UM, a transmitter HFNof the transmitter when the HFN de-synchronization condition is TRUE,wherein the adjusted transmitter HFN is used for new PDUs to betransmitted in the RLC UM.
 10. An apparatus for data communicationbetween a transmitter and a receiver in a radio link control (RLC)unacknowledged mode (UM), comprising: a memory coupled to the at leastone processor storing executable instructions; and a processor incommunication with the memory, wherein the processor is configured toexecute the instructions to: determine, by the transmitter operating inthe RLC UM, a hyper frame number (HFN) de-synchronization condition,wherein the HFN de-synchronization condition is FALSE when at least oneprotocol data unit (PDU) out of a plurality of successive PDUs issuccessfully transmitted by the transmitter to the receiver, wherein theHFN de-synchronization condition is TRUE when all of the plurality ofsuccessive PDUs are lost, and wherein a number of the plurality ofsuccessive PDUs is equal to a full cycle of RLC UM sequence numbers, amultiple of the full cycle of RLC UM sequence numbers, or a numbergreater than the full cycle of RLC UM sequence numbers; and adjust, bythe transmitter operating in the RLC UM, a transmitter HFN of thetransmitter when the HFN de-synchronization condition is TRUE, whereinthe adjusted transmitter HFN is used for new PDUs to be transmitted inthe RLC UM.
 11. An apparatus for data communication between atransmitter and a receiver in a radio link control (RLC) unacknowledgedmode (UM), comprising: means for determining, by the transmitteroperating in the RLC UM, a hyper frame number (HFN) de-synchronizationcondition, wherein the HFN de-synchronization condition is FALSE when atleast one protocol data unit (PDU) out of a plurality of successive PDUsis successfully transmitted by the transmitter to the receiver, whereinthe HFN de-synchronization condition is TRUE when all of the pluralityof successive PDUs are lost, and wherein a number of the plurality ofsuccessive PDUs is equal to a full cycle of RLC UM sequence numbers, amultiple of the full cycle of RLC UM sequence numbers, or a numbergreater than the full cycle of RLC UM sequence numbers; and means foradjusting, by the transmitter operating in the RLC UM, a transmitter HFNof the transmitter when the HFN de-synchronization condition is TRUE,wherein the adjusted transmitter HFN is used for new PDUs to betransmitted in the RLC UM.
 12. The apparatus of claim 11, wherein themeans for determining is further for: determining, by an RLC sub-layerof the transmitter, a successful or unsuccessful transmission status ofa PDU based on a transmission status of the PDU in a media accesscontrol (MAC) sub-layer; and mapping, by the RLC sub-layer, thesuccessful or unsuccessful transmission status to the plurality ofsuccessive PDUs.
 13. The apparatus of claim 12, wherein the transmissionstatus comprises a hybrid automatic repeat request (HARQ), wherein theMAC sub-layer provides a transmit status primitive to the RLC sub-layer,wherein the transmit status primitive indicates a status of a PDUtransmission.
 14. The apparatus of claim 12, wherein the datacommunication comprises an uplink communication from the transmitter tothe receiver, wherein the MAC sub-layer and the RLC sub-layer arecollocated at the transmitter, wherein the MAC sub-layer provides theHARQ to the RLC sub-layer via an inter-layer communication interfacebetween the MAC sub-layer and the RLC sub-layer.
 15. The apparatus ofclaim 12, wherein the data communication comprises a downlinkcommunication from the transmitter to the receiver, wherein the MACsub-layer provides the HARQ to the RLC sub-layer via a networkinter-layer communication between a first network entity and a secondnetwork entity, wherein the first network entity comprises the RLCsub-layer, and wherein the second network entity comprises the MACsub-layer.
 16. The apparatus of claim 11, wherein each one of thetransmitter or the receiver comprises a Node B, a user equipment, or anetwork entity.
 17. The apparatus of claim 11, wherein the means foradjusting adjusts the transmitter HFN to synchronize the transmitter HFNwith a receiver HFN of the receiver, wherein ciphering and decipheringparameters of the transmitter and the receiver are synchronized when thetransmitter and the receiver use a same HFN and a same′ RLC UM sequencenumber.
 18. The apparatus of claim 11, wherein the means for adjustingadjusts the transmitter HFN by decrementing the transmitter HFN.